1. Field of the Invention
The present invention relates to process and apparatus for the continuous extraction of oils and soluble substances from solid materials through the use of solvents and, more particularly, to the use of a multi-stage extraction system in which extraction of the oils, etc. is accomplished while the material is moved from one station to another during processing.
2. Prior Art
In the past, in order to increase the volume of material to be processed in solvent extraction equipment, which became necessary due to the ability of other equipment in the total processing system to handle greater volumes of processed material, it was necessary to increase the diameter of the cylindrical extractors since they were only single-stage extractors in which a plurality of baskets were disposed within a cylindrical housing in a circular pattern. This was acceptable until the diameters of the extractors became so large that they could not conveniently be shipped from the site of fabrication to the plant location where they would be utilized. This resulted in the necessity of some of the extractors being fabricated on site which was both costly and inconvenient.
This initial difficulty was substantially overcome by the introduction of multiple-stage cylindrical extractors such as are commonly referred to as the carousel-type extractor as illustrated, for example, by Depmer U.S. Pat. No. 3,131,202. In this type of extraction device a plurality of stages of extractors, each essentially identical to the prior art single-stage extractor, are stacked upon one another. The baskets in each section are then rotated through almost 360.degree. and then dumped into the subsequent baskets beneath, in sequence, and these are then again rotated so that the varying strengths of miscella and solvent can be applied to the baskets. In this manner, a higher volume of material can be processed merely by adding an additional stage to the extractor without increasing its diameter, which thus permits the extractors to be manufactured and shipped more easily.
Unfortunately, because of the substantial weight of the baskets containing the large volumes of material being processed, a substantial amount of energy is utilized to rotate these baskets.